ML20168A461
| ML20168A461 | |
| Person / Time | |
|---|---|
| Site: | Dresden  |
| Issue date: | 06/16/2020 |
| From: | Christopher Hunter NRC/RES/DRA/PRB |
| To: | |
| Littlejohn J (301) 415-0428 | |
| References | |
| LER 1971-LTR-00 | |
| Download: ML20168A461 (4) | |
Text
PRECURSOR DESCRIPTION AND DATA NSIC Accession Number:
39380 Date:
December 8, 1971
Title:
Safety Valve Operation After Feedwater Transient at Dresden 3 The failure sequence was:
- 2. The 3B feedwater pump auto-started and was used to recover water level.
- 3. The 3B feedwater regulating valve locked out in the open position and the flow on light failed to indicate~this situation.
- 4. Within 2 minutes and 45 seconds the water level had reached the main steam-line causing a safety valve to actuate which resulted in pressurizing the drywell.
- 5. During the transient low power range monitor cabling, one electromatic relief valve solenoid operator and piping insulation were damaged.
Corrective action:
- 1. All damaged equipment was repaired or replaced.
- 2. The feedwater control system was recalibrated and the signals verified.
- 3. The air system was modified by installing a 10 ft3 accumulator.
Design purpose of failed system or component:
The feedwater regulating valve controls the amount of feedwater supplied to the reactor.
Unavilailiy ofsysem er WSH 400 Unavailability of systoemt per WASH 1400:-
Unavailabilities are in units of per demand D-1.
Failure rates are in units of per hour HR-1
Condensate Booster Pump A Turbine Trip!
The B Feedwater Pump The Regulator Valve The Plant was Trip Causes Of Feed-Reactor Trip Auto Starts And Sup-Sticks Open And Brought To A water Transient Occurs plies Coolant To The Overf ills The Safe Shutdown IReactor Reactor Vessel.
I Water Blows Out I ________________________________________
___________________________The________
Th Relel V lvief________Valve_________
Potential Severe Core Damage No Yes No No, ECCS systems available No ATWS NSIC 39380 -
Actual Occurrence of Safety Valve Actuation After Feedwater Transient at Dresden 3
Excessive Coolant Reactor Scram Reactor Vessel Or Reactor Coolant Overflows Steam Line Break Long Term Inventory Turbine Isolate Into Steam Lines, Is Dis-Due To Turbine Core charged Through Relief Missiles, etc.
Cooling Valves, Which Stick Open Success Potential Severe Core Damage Small LOCA Initiator No Yes MSLB No No Yes Yes No Yes NSIC 39380 -
Sequence of Interest for Safety Valve Actuation After Feedwater Transient at Dresden 3
CATEGORIZATION OF ACCIDENT SEQUENCE PRECURSORS NSIC ACCESSION NUMhBER:
39380 DATE OF LER:
February 22, 1972 DATE OF EVENT: December 8, 1971 SYSTEM INVOLVED: Pressure Relief, Feedwater COMPONENT INVOLVED: Feedwater Regulator Valve CAUSE: A mechanical failure SEQUENCE OF INTEREST: Excessive Coolant Inventory Transient ACTUAL OCCURRENCE:
Safety valve operation after feedwater transient REACTOR NAME:
Dresden 3 DOCKET NUMBER:
50-249 REACTOR TYPE:
BW.R DESIGN ELECTRICAL RATING:
794 MWe REACTOR AGE:
0.94 yr VENDOR: General Electric ARCHITECT-ENGINEERS: Sargent & Lundy OPERATORS:
Cormmonwealth Edison LOCATION: Nine miles East of Morris, Ill.
DURATION:
N/A PLANT OPERATING CONDITION:
100% power SAFETY FEATURE TYPE OF FAILURE:
(a)inadequate performance; (b) failed to start; I~
P made inoperable; (d) ____________
DISCOVERY METHOD: operational transient COMMENT: